# year    value 
 1980 16.42892 
 1981 16.34761 
 1982 16.25659 
 1983 15.90877 
 1984 16.15681 
 1985 16.33017 
 1986 16.25021 
 1987 16.38041 
 1988 16.39489 
 1989  16.5019 
 1990 16.54343 
 1991 16.52903 
 1992 16.10607 
 1993 16.32473 
 1994 16.42839 
 1995 16.44888 
 1996  16.6237 
 1997 16.72146 
 1998  16.7075 
 1999 16.78523 
 2000 16.87884 
 2001 16.97766 
 2002 16.86044 
 2003 16.88202 
 2004 16.90436 
 2005 17.05399